Supertyphoon Forrest (September 1983): The Overlooked Record Holder of Intensification in 24, 36, and 48 h

Abstract

Reanalysis of aircraft reconnaissance data shows that in September 1983 Supertyphoon Forrest reached a sea level pressure of 876 hPa instead of 883 hPa as previously accepted. It is estimated that at the time, Forrest was the deepest typhoon in the western North Pacific since Tip, 870 hPa in October 1979, and June, 875 hPa in November 1975. Using calculations from 700-hPa aircraft reconnaissance data, it is determined that a surface pressure of 876 hPa was reached at 2030 UTC 22 September 1983, which would constitute an amazing deepening rate of 100 hPa in a little over 23 h. In addition, pressure drops of 101, 111, and 120 hPa in 24, 36, and 48 hrespectively, are inferred from these calculations. These figures would set new records previously held by Supertyphoons Ida in September 1958 and Irma in November 1971. The validity of using surface pressures calculated from 700-hPa data is discussed by comparing them with other data gathered in Supertyphoon Forrest as well as with comparisons from other aircraft reconnaissance data in similarly intense typhoons.